The present invention relates in general to an electric device for a motor vehicle and in particular to an unit for a central interconnection of electric components such as laced wiring harnesses, plug-in connectors, fuses, switching devices, electronic control devices for electric consumers in the car and the like.
Devices of this kind described for example in the German publication DE-GM 8034130, are generally called central electric units. They include a compact housing provided with solid conductive webs arranged at different levels.
Primarily, the function of the central electric unit is to distribute power or to branch electric current to different electric consuming circuits in a car, such as lamps, wipers, blinkers, heating, magnet valve and the like. There is also a possibility to use the central electric unit for monitoring the operational efficiency of respective consuming circuits and also for determining and signaling their malfunction. For this purpose, the electric consuming circuits are operated by switching devices which are mostly plugged into corresponding sockets in the upper side of the central electric unit. Cables or laced wiring harnesses, on the other hand, are usually attached by corresponding connectors to the lower side of the unit. In a known central electric unit, the plug in switching devices include frequently an electronic control circuit for operating the corresponding electric consuming circuits while the switching device itself is used in connection with a relay for turning on and off the consuming circuit.
The prior art arrangement of the central electric unit and the associated switching devices are expensive to manufacture. A separate electronic control circuit pertaining to a corresponding electric consuming circuit is associated with each switching device so that the manufacturing cost is further increased. Another disadvantage appears when the switching relay becomes damaged and the entire electronic control circuit must be discarded when the associated switching device is replaced. In addition in order to counteract voltage peaks, over voltage and negative pulses in the network of the motor vehicle, additional circuit adjustments and measures requiring further expensive component parts are necessary.